What is the pathophysiology of acute intermittent porphyria (AIP)?

Updated: Jul 08, 2020
  • Author: Thomas G DeLoughery, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Answer

AIP is an autosomal dominant disease that results from defects in the enzyme porphobilinogen-deaminase. This enzyme speeds the conversion of porphobilinogen to hydroxymethylbilane. In AIP, the porphyrin precursors, porphobilinogen and amino-levulinic acid (ALA), accumulate. The predominant problem appears to be neurologic damage that leads to peripheral and autonomic neuropathies and psychiatric manifestations. [2]

Although levels of porphobilinogen and ALA are always elevated during acute attacks, how this leads to the symptomatic disease is still unclear because most patients with the genetic defect have excessive porphyrin secretion but no symptoms.

A case-control study in 50 patients by Storjord et al found evidence that AIP is associated with systemic inflammation. Levels of prealbumin, C-peptide, and insulin, along with measures of kidney function, were all decreased in symptomatic patients, but not in asymptomatic ones. The decrease in C-peptide levels in symptomatic AIP cases indicates that reduced insulin release is associated with enhanced disease activity and reduction in kidney function. [3]


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